Wireless sensor node runs on harvested energy

An autonomous wireless temperature sensor powered by an 85μW piezoelectric generator has been developed.

Once the technology is mature it could be used in industrial applications such as tire-pressure monitoring and predictive maintenance of moving or rotating machine parts.

The sensor was built from standard components and then optimised to cut its power use from 1.5mW to ±10μW.

The vibrational energy harvester, built on a CMOS-compatible MEMS process, consists of a silicon mass suspended on a beam on to which a layer of aluminium nitride had been deposited to act as the piezoelectric material. By changing the dimensions of the beam and mass, the resonant frequency of the harvester can be adjusted between 150Hz and 1200Hz.

The harvesters are protected by being vacuum packed between two layers of glass. This also increases their output.

When the sensor node was subjected to 353Hz vibrations at accelerations of 0.64g, which the researchers claim represents the sort of vibrations the sensor would experience if mounted on an electrical machine, the generator delivered enough power to measure temperature and transmit it to a basestation in 15 seconds.

The work was done within the Micropower Program at Holst Centre, a collaboration between IMEC, the Belgian nanoelectronics research centre, and TNO, the Dutch independent research organisation.

The work was presented during the 2009 IEEE International Electron Devices Meeting in Baltimore this week.